1. Field of the Invention
The present invention relates to an image forming apparatus in which a power supply mode is shifted between a normal mode and a power saving mode (sleep mode or low power mode).
2. Description of Related Art
In general image forming apparatuses such as a multifunction peripheral and a printer, a power supply mode is shifted between a normal mode and a power saving mode. The normal mode refers to a mode in which power is supplied to each section of the apparatus to maintain a state that is ready for printing. On the other hand, the power saving mode refers to a mode in which power supply to the apparatus is partially stopped to reduce power consumption as compared to the normal mode. For example, in a case where there is no operation performed on the image forming apparatus for a predetermined period of time, the image forming apparatus shifts from the normal mode to the power saving mode, to thereby save power. In a case where there is any operation or input performed on the image forming apparatus during the power saving mode or when printing is performed based on image data received from a network, the image forming apparatus recovers from the power saving mode to the normal mode to enter the state that is ready for printing.
By the way, the image forming apparatus requires a certain length of preparation time to enter the state that is ready for printing after the apparatus starts recovery from the power saving mode to the normal mode or after the apparatus is activated (powered ON). Such a preparation time is most necessary for a fixing device, for example. Specifically, the fixing device requires a certain length of time (stabilizing time) to raise and stabilize the temperature of a heating roller up to a temperature necessary to fix a toner image (fixing temperature) by using a fixing heater that generates heat when supplied with power. In a case of a color image forming apparatus, in particular, a large quantity of heat is necessary in the toner image fixing process, and hence a relatively long period of time is necessary for the fixing device to enter the state that is ready for printing (ready for fixing). At this time, on an apparatus main body side, various kinds of processing such as control system initialization and memory initialization are necessary for recovery from the power saving mode to the normal mode. In a case where the stabilizing time of the fixing device is sufficiently long, the above-mentioned processing such as the control system initialization can be performed sufficiently by the time when the fixing device is stabilized, and hence there can arise no problem with the control.
In recent years, however, the fixing heater and the heating roller have improved to reduce the stabilizing time of the fixing device, and in some cases, there is being introduced a fixing device which enters the state that is ready for printing in a shorter period of time than a recovery time necessary for, for example, the control system initialization processing on the apparatus main body side. In a case of employing such a fixing device, if the recovery time of the control system is longer than the stabilizing time of the fixing device, printing cannot be performed until the control system recovers even though the fixing device is in the state that is ready for printing, with the result that user convenience is lowered. Therefore, reduction in recovery time of the control system is demanded.
In view of the above, in a conventional image forming apparatus, a dedicated control bus for a peripheral control section starts to operate in response to input from a reset section for initializing an arithmetic processing device at the time of power-ON, to thereby initialize the peripheral control section. As a result, the recovery time of the entire system is reduced. Note that, a program for controlling the operation of the dedicated control bus is stored in a nonvolatile memory. Further, in another conventional image forming apparatus, a nonvolatile memory for storing initial values of setting data of function blocks is provided to an integrated circuit for a peripheral control section separately from a register block for storing the setting data of the function blocks. The initial values are set at the same time as the recovery, and hence there is no need for a period of time necessary for the control program to initialize the integrated circuit for the peripheral control section, with the result that the system recovery time is reduced.
However, the above-mentioned conventional image forming apparatuses are configured on a premise of employing a fixing device having a small heat capacity and requiring a sufficiently short stabilizing time from the start of power supply to the fixing heater until the temperature reaches to the fixing temperature. Such a fixing device is more expensive than an ordinary fixing device having large heat capacity because a special fixing heater and a special heating roller are employed. As a result, cost for the entire apparatus increases. Further, in the case of employing the fixing device having a small heat capacity, the above-mentioned nonvolatile memory is necessary to reduce the initialization time of the control system, and hence a further increase in cost for the entire apparatus is inevitable.
As described above, in the conventional image forming apparatuses, higher user convenience is sought by reducing the system recovery time, and hence the cost for the entire apparatus is not taken into consideration. There is a demand for an image forming apparatus having such a configuration that may achieve cost reduction and higher user convenience without employing the special fixing device having a small heat capacity.
In recent years, power saving has been demanded for electrical apparatuses, and also in the image forming apparatus, reduction in power consumption has become more important. However, when the effect of reducing the power consumption is extremely sought in the configuration employing the low-cost fixing device having a large heat capacity, the user convenience may be lowered conversely.
Specifically, in the fixing device having a large heat capacity, even if the fixing heater is turned OFF after the printing is finished, a certain quantity of heat remains. Hence, in a case where the apparatus recovers to the normal mode immediately after the fixing heater is turned OFF and the apparatus shifts to the power saving mode, the fixing heater is turned ON and in no time the temperature of the heating roller reaches to the fixing temperature. In this case, when, for example, power supply to all the function blocks is turned OFF at the same time as the shift from the normal mode to the power saving mode so as to increase the effect of reducing the power consumption in the power saving mode, all the function blocks need to recover at the time of recovery to the normal mode, and hence a long recovery time is necessary. Consequently, printing cannot be performed even though the fixing device is in the state that is ready for printing on ahead, with the result that the user convenience is lowered.
Therefore, in the case of employing the low-cost fixing device having a large heat capacity, in view of the remaining heat after the fixing heater is turned OFF, there is a demand for such a configuration that the effect of enhancing the user convenience by reducing the recovery time to the normal mode, and the effect of reducing the power consumption in the power saving mode can be obtained in a balanced manner.